The primary structures of growth hormones and prolactins from species repesenting all classes of vertebrates will be investigated. Automatic sequencing together with manual techniques will be used. A correlation of structure and biological activity will be attempted, with emphasis on the overlap of lactogenic and growth promoting properties. The structures of the family of proteins that make up human growth hormone will be determined. Growth promoting and lactogenic activities will be measured for each of the components. Assays to be used will be the pigeon crop sac, rabbit intraductal mammary gland, rat tibial line and radioimmunoassay. The structure of the diabetogenic substance that is a common contaminant of human growth hormone will be investigated. Sequencing will be done by both automatic and manual techniques.